Thyrotoxicosis considerably increases the demand for thiamine. In vivo study in a rat model demonstrated that thyroid hormones have a direct influence on mitochondria which is the main source of energy. Thiamine in its various forms functions as an important coenzyme for macronutrient oxidation and the production of adenosine triphosphate. Thiamine pyrophosphate works in several oxidative decarboxylation reactions and is a catalyst in the reactions of Krebs cycle. Therefore, thiamine seems to decrease in the case of an increased tissue metabolism. In the previous case reports, they described the possible association between thyrotoxicosis and thiamine deficiency in patients manifested as Wernicke-Korsakoff syndrome.